Comparative Torque and Horsepower Requirements of Standard Four-Flute and Spiral-Flute Taps

Abstract

Abstract This paper reports certain tapping tests performed as a part of a research project of the Iowa Engineering Experiment Station at Iowa State College. Data are presented on the torque and horsepower requirements for the use of ½-in., 13-thread, standard-flute, and spiral-tip flute taps during the tapping of S.A.E. 1020 steel. The torque values are shown to vary with speed when a constant percentage of thread is produced. The torque increased with speed when lard oil was used as a cutting fluid; the tendency was toward decreased torque with increased speed when sulphurized oil was used. Spiral-tip taps required less torque than straight-flute taps at similar cutting conditions. Horsepower requirements were found to be less with sulphurized oil than with lard oil at high percentages of thread depths for both kinds of taps. Spiral-tip taps could be operated at lower horsepower inputs than could the straight-flute style when similar cutting conditions exist. Another series of tests pertains to the dry tapping of cast iron with ⅜-in., 16-thread taps. There was little difference in the torque requirements when the two types of taps were used. Slightly lower horsepower input is shown for the spiral-tip tap.